[Proposal] Async methods chaining

[litichevskiydv]

There is a class which methods return Task<> with this class as a generic parameter

public class Builder
{
	public Task<Builder> PerformFirstStep(...)
	{
		...
	}
	
	public Task<Builder> PerformSecondStep(...)
	{
		...
	}
}

so we ought to write code in such way

builder = await builder.PerformFirstStep(...);
builder = await builder.PerformSecondStep(...);

That is why I think sugar like

builder = await builder
			.PerformFirstStep(...)
			.PerformSecondStep(...);

will be useful.

[iam3yal]

Dup #827.

p.s. What's going on with all these chaining proposals nowadays? 😆

[litichevskiydv]

@eyalsk, I like fluent syntax) I've even implemented it once in pet project with helper

public class FluentChainedTask<TApiFluentClient> : DynamicObject where TApiFluentClient : BaseFluentClient
{
    private readonly Task<TApiFluentClient> _task;

    public FluentChainedTask(Task<TApiFluentClient> task)
    {
        _task = task;
    }

    public TaskAwaiter<TApiFluentClient> GetAwaiter()
    {
        return _task.GetAwaiter();
    }

    public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, out object result)
    {
        var methodInfo = typeof(TApiFluentClient).GetTypeInfo().GetDeclaredMethod(binder.Name);
        if (methodInfo == null)
            return base.TryInvokeMember(binder, args, out result);

        result = new FluentChainedTask<TApiFluentClient>(
            _task
                .ContinueWith(t =>
                              {
                                  try
                                  {

                                      return (Task<TApiFluentClient>) methodInfo.Invoke(t.Result, args);
                                  }
                                  catch (TargetInvocationException ex)
                                  {
                                      ExceptionDispatchInfo.Capture(ex.InnerException).Throw();
                                  }
                                  return null;
                              })
                .Unwrap());
        return true;
    }
}

however without support from language I lost IntelliSense.

[iam3yal]

@litichevskiydv

I like fluent syntax)

See this is the problem I have with it, you actually write code, not because you need to do it but because you like the looks of it, I don't get it.

[juepiezhongren]

@eyalsk it is the same of needing abr for await
@litichevskiydv #827